This present invention relates to a lead assembly including an electrode which is adapted for connecting a living organ to an electrical device. In one embodiment, the subject invention is adaptable for a pacing and sensing lead assembly which is transvenously implantable for connecting a heart pacemaker device and cardiac tissue.
In pacemaker technology and related arts, a body implanted, intravascular lead assembly is oftentimes used which comprises an electrical conductor which, at its distal end, is adapted to be suitably connected to a source of electrical energy. The assembly further includes an electrode means at the other end of the conductor which is adapted to be secured to tissue. With pacemakers, an intravenous transplantation method may be utilized to install the lead assembly. With this method, which may be made under local anesthesia, the electrode means is pushed into the heart through a vein.
In a typical lead assembly for use in the above purposes, the lead assembly of an electrical conductor and electrode means affixed to the end of the conductor is adapted to be firmly lodged in and permanently secured to or removeable from tissue inside the body at a desired location. The conductor and the portion of the electrode means affixed to the conductor are sealed from body fluids and tissue by a material substantially inert to body fluids and tissue. Sheath means are provided for permitting the lead and electrode means to be inserted into and guided through a body vessel to a position inside the body without causing injury to the body vessel and for permitting the electrode means to be firmly lodged in and permanently secured to body tissue. The electrode of the lead assembly may be firmly anchored to tissue such as the heart muscle by mechanical fixation devices such as metal or plastic hooking devices and, in one known embodiment, by a helix of suitable electrode material within the sheath of the lead assembly.
A typical lead assembly for the above-mentioned purposes is exemplified in DE-05 30 20 584 and this assembly includes a blocking mechanism which blocks the store by means of an additional blocking wire or thread. Such a blocking wire or thread may be operated from the distal end of the lead assembly and unlocked by being pulled out of the electrode lead. Such a blocking wire or thread is difficult to use since space required for this purpose is not available.
Another lead assembly as is disclosed in U.S. Patent No. 4,106,512 to Bisping, incorporated by reference herein in its entirety, has a flexible helical conductor whose end has a lapse helix. Force exerted from the proximal end causes axial movement such that the conductor can be either extracted from or screwed into the tissue. With this type of lead assembly where the forces must be exerted from the proximal end, difficulties may be encountered in that, due to the tension forces along the electrical conductor and the insulating sheath, dislocation of the electrode head can occur during fixation of the conductor. Manipulation of the electrode head during fixation is, of course, not particularly desireable.